The present invention relates to a mechanical coupling and more specifically to a coupling for use with machine tools rotating at high speeds.
Machining operations using high-speed rotating tooling are becoming more prevalent in industry. Such operations include, among other things, milling, drilling and boring. As an example, in drilling operations, a disposable tool such as a high-speed drill is used and provides easy insertion in and removal from a chuck when the drill needs to be reconditioned or replaced. It would be common for a machine operator to have an inventory of replacement drills so that the drilling operation would not be interrupted while a single drill bit is reconditioned or replaced. On the other hand, some rotating tooling used in machining operations is much more expensive than a single drill bit and becomes uneconomical to maintain a large inventory of parts.
One such example is the milling cutter 10 shown in FIG. 1. A typical milling cutter 10 is comprised of a shank 20 with an integral head 30 defining a back end 40 and a front end 50. Within the head 30 at the front end 50 are located a plurality of cutting inserts 60 mounted about the periphery of the head 30 and secured to the head with retaining screws 70. A flat 80 may be present on the shank 20 in order to provide a flat surface to grasp the shank 20 for imparting rotational motion into the milling cutter 10 in the performance of a milling operation. Unlike a drill used for boring holes within a material, a milling cutter 10 such as that shown in FIG. 1 would be used for an operation similar to that of planing in woodwork whereby the milling cutter 10 removes a layer of material along a plane perpendicular to the cutter axis. The milling cutter 10 is held and driven by a mechanism which securely grasps the shank 20 and imparts rotation.
The cutting edges of the cutting inserts 60 typically wear or break thereby requiring reindexing or replacement of insert 60. Cutting insert 60 in FIG. 1 is seen to be four-sided and, as such, may be indexed to expose unused edges to the workpiece. The milling cutter head 30 may also be damaged in a manner which requires the entire milling cutter 10 to be replaced. As such, there are occasions that require the milling cutter to be removed from the machine. While it would be preferred to have a plurality of milling cutters available in inventory, the cost of an individual cutter may be fairly expensive such that this would not be practical.
One solution to this problem would be to provide a milling cutter having a removable head such that an inventory of replacement heads with cutting inserts already attached would be available at any given time. In this manner, only a single shank of the milling cutter with a plurality of replacement heads would be required. This would alleviate the need to maintain an inventory of entire milling cutters. Additionally, if the head became damaged beyond repair, a savings may be realized by replacing the head rather than the entire milling cutter.
However, under such circumstances it would be important to secure the head to the shank in a manner closely resembling the configuration of the original milling cutter 10 thereby providing correct centering and alignment of the head relative to the shank. This is especially important when high speed milling cutters are utilized because any misalignment or improper positioning of the head relative to the shank could create an imbalanced condition of the tool which would be aggravated by the high rotational velocity of the tooling.
An object of this invention is to provide a replaceable head for a milling cutter shank thereby alleviating the need to replace the entire milling cutter.
Another object of the invention is to provide a simple and economical replaceable head for a milling cutter whereby an inventory of heads may be supplied at a reasonable cost.
Another object of this invention is to provide a replaceable head for a milling cutter which tends to be self-centering during high-speed operations.
Another object of the invention is to provide a coupling device which tends to become self-centered to a higher degree with increasing rotational velocity of the coupling device.
Another object of the invention is to provide a coupling device that when rotated at high speeds tends to be self-balancing.
Still another object of this invention is to provide a milling cutter capable of operation at high speeds in which a replaceable head may be easily installed or removed from the shank.